______________________________________                                           Central Body 22Central Body 22                                                Height (z-axis)                                                                      Length (y-axis)                                         ______________________________________                                    1        0.23 inch (5.8 mm)                                                                     0.45 inch (11.5 mm)                                 2        0.23 inch 5.8 mm)                                                                      0.74 inch (18.8 mm)                                 3        0.31 inch (7.9 mm)                                                                     0.45 inch (11.5 mm)                                 4        0.31 inch (7.9 mm)                                                                     0.74 inch (18.8 mm)                                 5        0.38 inch (9.7 mm)                                                                     0.45 inch (11.5 mm)                                 6        0.38 inch (9.7 mm)                                                                     0.74 inch (18.8 mm)                                 ______________________________________

Generally speaking, regardless of the exact size of thecentral body 22, the first and

second tabs

24, 26 have approximately the same dimensional characteristics. In this regard, each of the first and

second tabs

24, 26 has a height (z-axis) of approximately 0.12 inch (≈3.0 mm) and a length (y-axis) of approximately 0.20 inch (≈5 mm).

B. Trial Implant 60

As previously described, thetrial implant 20 is preferably shaped to imitate the shape of an available prosthetic spinal disc nucleus. One example of the prostheticspinal disc nucleus 50 was shown in FIG. 1C as being generally rectangular. A variety of differently shaped prosthetic disc nuclei are also available. As a result, thetrial implant 20 can be modified to simulate these other shapes. One example of an alternative embodiment,trial implant 60 is shown in FIG. 2. Similar to the trial implant 20 (FIG. 1), the alternativeembodiment trial implant 60 is preferably comprised of an elongatedcentral body 62, afirst tab 64 and asecond tab 66. Thefirst tab 64 and thesecond tab 66 extend from opposite sides of thecentral body 62.

Thecentral body 62 defines asuperior face 68, aninferior face 70, ananterior side face 72, aposterior side face 74, afirst end face 76 and asecond end face 78. As shown more clearly in FIGS. 2A and 2B, thecentral body 62 is fabricated to assume a tapered, rectangular shape. For purposes of identification, then, thetrial implant 60 can be referred to as a "tapered trial implant," whereas the trial implant 20 (FIG. 1) can be referred to as a "rectangular trial implant." With respect to the taperedtrial implant 60, a top view (FIG. 2A) shows thesuperior face 68 as being substantially rectangular. In one preferred embodiment, theinferior face 70 is virtually identical to thesuperior face 68. Additionally, a side view (FIG. 1B) depicts thesecond end face 78 as tapered or wedge shaped. Thefirst end face 76 is preferably virtually identical to thesecond end face 78.

With reference to FIG. 2A, the top view of the taperedtrial implant 60 defines a width (x-axis in FIG. 2A) and length (y-axis in FIG. 2A). Further, the side view of the taperedtrial implant 60 defines the width (x-axis in FIG. 2B) and a height (z-axis in FIG. 2B). As shown in FIG. 2B, thecentral body 62 has a height (z-axis) increasing from the posterior side face 74 to theanterior side face 72. With reference to FIG. 2B, thecentral body 62 is formed such that each of thesuperior face 68 and theinferior face 70 form an angle relative to the posterior side face 74 in the range of approximately 92-100 degrees such that thecentral body 62 has an included angle in the range of 4-20 degrees, preferably 12 degrees.

Thecentral body 62 is virtually identical to the central body 22 (FIG. 1) previously described in terms of construction. Thus, thecentral body 62 is preferably made of a rigid, surgically safe material able to maintain its structural integrity when subjected to repeated sterilization, such as with an autoclave Further, the various faces 68-78 are all relatively smooth to facilitate insertion of the taperedtrial implant 60 into a nucleus cavity (not shown).

Thefirst tab 64 and thesecond tab 66 are virtually identical, each including anopening 80. Thefirst tab 64 and thesecond tab 66 extend from opposite sides of thecentral body 62. For example, thefirst tab 64 extends from thefirst end face 76; whereas thesecond tab 66 extends from thesecond end face 78. As described in greater detail below, thefirst tab 64 and thesecond tab 66 are configured to facilitate retrieval of thetrial implant 60 from an enclosed area, such as a nucleus cavity, and therefore are correctly referred to as retrieving means. Similar to thecentral body 62, the first and

second tabs

64, 66 are preferably made of a rigid, surgically safe material able to maintain structural integrity when subjected to repeated sterilization (such as with an autoclave). Additionally, the first and

second tabs

64, 66 are configured to reflect sizing characteristics of an available prosthetic spinal disc nucleus, as described in greater detail below.

Comparison of the taperedtrial implant 60 of FIG. 2 with the tapered prostheticspinal disc nucleus 90 of FIG. 2C illustrates the general correspondence in size and shape of the taperedtrial implant 60 with the tapered prosthetic spinal disc nucleus 90 (preferably in the dehydrated state). In a preferred embodiment, the first and

second tabs

64, 66 correspond with theclosures 96 of the tapered prostheticspinal disc nucleus 90. It should be understood that the tapered prostheticspinal disc nucleus 90 shown in FIG. 2C is but one example of an available prosthesis. Other prosthetic nucleus devices are available that vary in size and construction from the one depicted in FIG. 2C. The taperedtrial implant 60 may be configured to correlate with the specific size and shape characteristics of these varying prostheses. In this regard, the first and

second tabs

64, 66 may be eliminated.

With the above design characteristics of the taperedtrial implant 60 in mind, in one preferred embodiment the taperedtrial implant 60 has an overall length in the range of 0.5-1.6 inch (≈12.5-40.5 mm). Thecentral body 62 has a length (y-axis in FIG. 2A) in the range of approximately 0.3-1.0 inch (≈7.5-25.5 mm)and a width (x-axis in FIG. 2A) in the range of approximately 0.3-0.7 inch (≈7.5-18 mm). As shown in FIG. 2B, the height (z-axis) of thecentral body 62 tapers from a maximum height at the anterior side face 72 to a minimum height at theposterior side face 74. With this construction in mind, in a preferred embodiment, thecentral body 62 has a maximum height (or anterior side face 72 height) in the range of approximately 0.1-0.5 inch (2.5-12.5 mm)and a minimum height (or posterior side face 74 height) in the range of approximately 0.05-0.4 inch (≈1-10 mm). The first and

second tabs

64, 66 are virtually identical, having a length (y-axis in FIG. 2A) in the range of approximately 0.1-0.3 inch (≈2.5-7.5 mm) and a height (z-axis in FIG. 2B) in the range of approximately 0.1-0.2 inch (≈2.5-5 mm). It should be recognized that the above-provided dimensions can vary widely such that the taperedtrial implant 60 is sized to evaluate any individual disc space.

Once again, the taperedtrial implant 60 is preferably configured to match the size and of an available prosthetic spinal disc nucleus, such as the tapered prosthetic spinal disc us 90 shown in FIG. 2C. Due to the variations in size of individual disc spaces, the ed prostheticspinal disc nucleus 90 is made available to a surgeon in different sizes. As a result, the taperedtrial implant 60 should also be fabricated in a number of different sizes. In one preferred embodiment, at least six different sizes of the taperedtrial implant 60, and in particular thecentral body 62, are available. In this regard, thecentral body 62 has a width is in FIG. 2B) of approximately 0.5 inch (≈13 mm), in conjunction with varying length height dimensions in accordance with the following table:

______________________________________                                    Central Body 62Central Body 62Central Body 62                                Maximum Height                                                                          Minimum Height                                                                         Length                                         (z-axis)      (z-axis)     (y-axis)                                       ______________________________________                                    1   0.22 inch (5.6 mm)                                                                      0.12 inch (3.0 mm)                                                                     0.55 inch (14.0 mm)                        2   0.22 inch (5.6 mm)                                                                      0.12 inch (3.0 mm)                                                                     0.74 inch (18.8 mm)                        3   0.29 inch (7.4 mm)                                                                      0.19 inch (4.8 mm)                                                                     0.55 inch (14.0 mm)                        4   0.29 inch (7.4 mm)                                                                      0.19 inch (4.8 mm)                                                                     0.74 inch (18.8 mm)                        5   0.37 inch (9.4 mm)                                                                      0.27 inch (6.9 mm)                                                                     0.55 inch (14.0 mm)                        6   0.37 inch (9.4 mm)                                                                      0.27 inch (6.9 mm)                                                                     0.74 inch (18.8 mm)                        ______________________________________

Regardless of the exact size of thecentral body 62, the first and

second tabs

64, 66 are virtually identical, having a length (y-axis) of approximately 0.20 inch (≈5 mm) and a axis) of approximately 0.12 inch (≈3.0 mm). Finally, theopening 80 associated thefirst tab 64 and thesecond tab 66 has a diameter of approximately 0.10 inch (≈2.5 mm).

C. Trial Implant 100

Yet another alternative embodiment of atrial implant 100 is shown in FIGS. 3-3B. Thetrial implant 100 is highly similar to previous embodiments and includes acentral body 102, afirst tab 104 and asecond tab 106. Once again, thecentral body 102 defines asuperior face 108, aninferior face 110, ananterior side face 112, aposterior side face 114, afirst end face 116 and asecond end face 118. Thefirst tab 104 and thesecond tab 106 extend from thefirst end face 116 and thesecond end face 118, respectively.

The composition and structure of thecentral body 102, thefirst tab 104 and thesecond tab 106 are virtually identical to those previously described with reference to the rectangular trial implant 20 (FIG. 1) and the tapered trial implant 60 (FIG. 2). The actual shape, however, of these components differs somewhat. In particular, thetrial implant 100 assumes an angled, wedge-shaped, best shown in FIGS. 3A and 3B. For this reason, thetrial implant 100 can be referred to as an "angled trial implant."

Theangled trial implant 100 tapers in height (z-axis in FIG. 3B) from theposterior side face 114 to theanterior side face 112. Similar to the tapered trial implant 60 (FIG. 2), the first and second end faces 116, 118 each of theangled trial implant 100 are angled to form an included angle in the range of approximately 4-20 degrees, preferably 12 degrees. Additionally, thecentral body 102 tapers in length (y-axis in FIG. 3A) from theposterior side face 114 to theanterior side face 112 such that the superior and

inferior faces

108, 110 are approximately trapezoidal. In particular, with reference to FIG. 3A, thecentral body 102 tapers in length (y-axis) between theanterior side face 112 and theposterior side face 114 to form an included angle in the range of approximately 40-60 degrees, preferably 50 degrees. It should be understood, however, that other angles, either greater or smaller, are also acceptable. Additionally, thesuperior face 108 and theinferior face 110 need not be identical.

The first and

second tabs

104, 106 are preferably virtually identical, configured to be parallel to the first and second end faces 116, 118, respectively. For example, as best shown in FIG. 3A, thefirst tab 104 has a generally uniform length (y-axis) that is parallel to the orientation of thefirst end face 116. Thesecond tab 106 has a similar relationship with respect to thesecond end face 118. Finally, the first and

second tabs

104, 106 each include anopening 120.

As with previous embodiments, theangled trial implant 100 is preferably sized and shaped to generally correspond with the size and shape of an available prosthetic spinal disc nucleus. An example of one such angled prostheticspinal disc nucleus 130 is shown in FIG. 3C. The angled prostheticspinal disc nucleus 130 is generally comprised of ahydrogel core 132 and a constrainingjacket 134. The constrainingjacket 134 is secured about thehydrogel core 132 byclosures 136 located at opposite ends of thehydrogel core 132. Thehydrogel core 132 is pre-formed to assume an angled, tapered shape, and is configured to expand from a dehydrated state to a hydrated state. The constrainingjacket 134 constrains expansion of thehydrogel core 132 in the hydrated state. The angled prostheticspinal disc nucleus 130 is typically implanted in the dehydrated state, and can be fabricated to various dimensions while still maintaining the depicted angled shape.

Comparison of thetrial implant 100 of FIG. 3 with the angled prostheticspinal disc nucleus 30 of FIG. 3C illustrates the general correspondence of the size and shape of theangled trial implant 100 with the angled prosthetic spinal disc nucleus 130 (preferably in the dehydrated state). Because theangled trial implant 100 is representative of the angled prostheticspinal disc nucleus 130 in terms of shape and size, theangled trial implant 100 can be used to evaluate whether the angled prostheticspinal disc nucleus 130 is of an appropriate size for a particular disc space. In this regard, it should be noted that the first and

second tabs

104, 106 correspond to theclosures 136. It should be understood that the angled prostheticspinal disc nucleus 130 shown in FIG. 3C is but one example of an available prosthesis. Other prosthetic nucleus devices are available that vary in size and construction from the one depicted in FIG. 3C. Theangled trial implant 100 may be configured to correlate with the specific size and shape characteristics of these varying prostheses. As a result, depending on the particular design of the prosthesis, the first and/or

second tabs

104, 106 may be eliminated from the angledtrial implant 100.

In light of the above preference that theangled trial implant 100 conform to an available prosthesis, such as the angled prostheticspinal disc nucleus 130 of FIG. 3C, certain dimensional attributes can be ascribed to one preferred embodiment of theangled trial implant 100. For example, theangled trial implant 100 tapers in length (y-axis in FIG. 3A) and has a maximum length (at theposterior side face 114 and including the first andsecond tabs 104, 106) in range of approximately 0.8-1.7 inches (≈20-43 mm), and a minimum length (at theanterior side face 112 and including thetabs 104, 106) in the range of approximately 0.4-1.2 inches (≈10-30.5 mm). As with previous embodiments, thecentral body 102 dictates the critical dimensions of theangled trial implant 100. Thecentral body 102 tapers in height (z-axis in FIG. 3B), having a maximum height (at the posterior side face 114) in the range of approximately 0.10-0.50 inch (≈2.5-12.5 mm)and a minimum height (at the anterior side face 112) in the range of approximately 0.02-0.37 inch (≈0.5-9.5 mm). Further, thecentral body 102 has a width in the range of approximately 0.3-0.7 inch (≈7.5-17.5 mm). Finally, thecentral body 102 tapers in length (y-axis in FIG. 3A), having a maximum length (at the anterior side face 112) in the range of approximately 0.6-1.1 inches (≈15-28 mm) and a minimum length (at the posterior side face 114) in the range of approximately 0.2-0.6 inch (≈2.5-5 mm). The first and

second tabs

104, 106 are virtually identical, each having a length (y-axis in FIG. 3A) in the range of approximately 0.1-0.3 inch (≈2.5-7.5 mm)and height in the range of approximately 0.1-0.2 inch. It should be recognized, however, that the above-provided dimensions can vary widely such that theangled trial implant 100 is sized to evaluate any individual disc space.

Because theangled trial implant 100 is sized to simulate an available prosthesis, such as the angled prostheticspinal disc nucleus 130 shown in FIG. 3C, theangled trial implant 100 is preferably made available to a surgeon in a variety of sizes. For example, in one preferred embodiment, thecentral body 102 of theangled trial implant 100 can be provided in at least three different sizes, set forth in the following table:

__________________________________________________________________________Central Body 102Central Body 102Central Body 102Central Body 102                             Maximum Height                                                                       Minimum Height                                                                     Maximum Length                                                                     Minimum Length                               (z-axis)   (z-axis) (y-axis) (y-axis)                                     __________________________________________________________________________1 0.23 inch (5.8 mm)                                                                 0.13 inch (3.3 mm)                                                                 0.85 inch (21.6 mm)                                                                0.40 inch (10.2 mm)                          2 0.29 inch (7.4 mm)                                                                 0.19 inch (4.8 mm)                                                                 0.85 inch (21.6 mm)                                                                0.40 inch (10.2 mm)                          3 0.37 inch (9.4 mm)                                                                 0.27 inch (6.9 mm)                                                                 0.85 inch (21.6 mm)                                                                0.40 inch (10.2 mm)                          __________________________________________________________________________

Regardless of the exact dimensions of thecentral body 102, the first tab and the

second tab

104, 106 are preferably virtually identical, having a preferred length (y-axis) of 0.2 inch (≈5 mm) and a preferred height (z-axis) of 0.12 inch (≈3 mm).

D. Trial Implant 140

Yet another alternative embodiment of atrial implant 140 is shown in FIGS. 4B. Thetrial implant 140 is similar to previous embodiments and includes acentral body 142, afirst tab 144 and asecond tab 146. Once again, thecentral body 142 defines asuperior face 148, aninferior face 150, ananterior side face 152, aposterior side face 154, afirst end face 156 and asecond end face 158. Thefirst tab 144 extends from thefirst end face 156, whereas thesecond tab 146 extends from thesecond end face 158. The first and

second tabs

144, 146 are virtually identical, each including ahole 160.

The composition and structure of thecentral body 142, thefirst tab 144 and thesecond tab 146 are virtually identical to those previously described, with reference to therectangular trial implant 20 of (FIG. 1), the tapered trial implant 60 (FIG. 2), and the angled trial implant 100 (FIG. 3). The actual shape, however, of the components differs somewhat. Thetrial implant 140, and in particular thecentral body 142, assumes an angled, wedge-shape. With reference to FIGS. 4A and 4B, this configuration has a reverse angular shape when compared to the angled trial implant 100 (FIG. 3). For this reason, thealternative trial implant 140 can be referred to as a "reverse angled trial implant."

The reverse angledtrial implant 140 again tapers in length (y-axis in FIG. 4A) from theposterior side face 154 to theanterior side face 152 such that the superior and

inferior faces

148, 150 are approximately trapezoidal. In particular, with reference to FIG. 4A, the reverse angledtrial implant 140 tapers in length between theposterior side face 154 and theanterior side face 152 to form an included angle in the range of approximately 40-60 degrees, preferably 50 degrees. It should be recognized, however, that other angles, either greater or smaller, are also acceptable. Additionally, the anterior and posterior side faces 152, 154 need not be identical or even symmetrical.

With reference to FIG. 4B, the reverseangle trial implant 140 also tapers in height (z-axis in FIG. 4B) from theanterior side face 152 to theposterior side face 154. In a preferred embodiment, thecentral body 142 tapers in height to form an included angle in the range of approximately 4-20 degrees, preferably 12 degrees. Other dimensions are acceptable, and thesuperior face 148 and theinferior face 150 need not be symmetrical.

In general terms, the reverseangle trial implant 140 is preferably sized and shaped to generally correspond with the size and shape of an available prosthetic spinal disc nucleus. An example of one such reverse angle prostheticspinal disc nucleus 170 is shown in FIG. 4C. The reverse angle prostheticspinal disc nucleus 170 is generally comprised of a hydrogel core 172 and a constrainingjacket 174. The constrainingjacket 174 secured about the hydrogel core 172 byclosures 176 located at opposite sides of the hydrogel core 172. The hydrogel core 172 is pre-formed to assume a reverse angled shape, and is configured to expand from a dehydrated state to a hydrated state. The constrainingjacket 174 constrains expansion of the hydrogel core 172 in the hydrated state. The reverse angled prostheticspinal disc nucleus 170 is typically implanted in the dehydrated state, and can be fabricated to various dimensions while still maintaining the depicted reverse angle shape.

Comparison of the reverseangle trial implant 140 of FIG. 4 with the reverse angle prostheticspinal disc nucleus 170 of FIG. 4C illustrates the general correspondence in size and shape of the reverseangle trial implant 140 with the reverse angle prosthetic spinal disc nucleus 170 (preferably in the dehydrated state). Because of this relationship, the reverseangle trial implant 140 can be used to evaluate whether the reverse angle prostheticspinal disc nucleus 170 is of an appropriate size for a particular disc space. In this regard, it should be noted that the first and

second tabs

144, 146 are representative of theclosures 176. It should be understood, however, that the reverse angle prostheticspinal disc nucleus 170 shown in FIG. 4C is but one example of an available prosthesis. Other prosthetic nucleus devices are available that vary in size and construction from the one shown in FIG. 4C. Depending upon the particular prosthesis in question, the first and/or

second tabs

144, 146 may be eliminated from the reverseangle trial implant 140.

Given the above preference that the reverseangle trial implant 140 correspond to a size and shape of the reverse angle prostheticspinal disc nucleus 170, certain dimensions can be attributed to the reverseangle trial implant 140. For example, in one preferred embodiment, the reverseangle trial implant 140 tapers in length (y-axis in FIG. 4A) and has an overall maximum length at theposterior side face 154 and including the

tabs

144, 146 in the range of approximately 0.92-1.6 inches (≈23.5-40.5 mm) and an overall minimum length (at theanterior side face 152 and including thetabs 144, 146) in the range of approximately 0.5-1.1 inches (≈12.5-28 mm). As with previous embodiments, thecentral body 142 dictates the critical dimensions of the reverseangle trial implant 170. Thecentral body 142 tapers in length (y-axis in FIG. 4A), having a maximum length (at the posterior side face 154) in the range of approximately 0.6-1.0 inch (≈15-25.5) and a minimum length (at the anterior side face 152) in the range of approximately 0.2-0.6 inch (≈5-15 mm). Further, thecentral body 142 tapers in height (z-axis in FIG. 4B), having a maximum height (at the anterior side face 152) in the range of approximately 0.1-0.5 inch (≈2.5-12.5 mm) and a minimum height (at the posterior side face 154) in the range of approximately 0.05-0.25 inch (≈1-6.5 mm). Finally, thecentral body 142 has a width in the range of approximately 0.3-0.7 inch (≈7.5-18 mm). The first and

second tabs

144, 146 have dimensions similar to those previously described with other embodiments of the present invention.

Because a surgeon is normally provided with different sized reverse angledprosthetic disc nuclei 170, the reverseangle trial implant 140 should also be provided in a variety of sizes. For example, one preferred embodiment of the present invention envisions at least three different reverseangle trial implants 140, having thecentral body 142 sized in accordance with the following table:

__________________________________________________________________________Central Body 142Central Body 142Central Body 142Central Body 142                            Maximum Height                                                                       Minimum Height                                                                     Maximum Length                                                                      Minimum Length                              (z-axis)   (z-axis) (y-axis)  (y-axis)                                    __________________________________________________________________________1 0.225 inch (5.7 mm)                                                                0.125 inch (3.2 mm)                                                                0.853 inch (21.7 mm)                                                                0.400 inch (10.2 mm)                        2 0.285 inch (7.2 mm)                                                                0.185 inch (4.7 mm)                                                                0.853 inch (21.7 mm)                                                                0.400 inch (10.2 mm)                        3 0.365 inch (9.3 mm)                                                                0.265 inch (6.7 mm)                                                                0.853 inch (21.7 mm)                                                                0.400 inch (10.2 mm)                        __________________________________________________________________________

E.Trial Implant Kit 180

Trial implants in accordance with the present invention have been described as having a wide variety of sizes and shapes, with each shape being representative of an available prosthetic nucleus. As described in greater detail below, during use, a particular trial implant can be used to evaluate whether an associated prosthetic nucleus will "fit" within a particular disc space. To facilitate this procedure, a wide variety of trial implants are preferably provided to a surgeon in a singular kit. One example of atrial implant kit 180 is shown in FIG. 5. Thetrial implant kit 180 includes acontainer 182 and a plurality oftrial implants 184. The plurality oftrial implants 184 are selectively maintained within thecontainer 182 for retrieval by a user (not shown). In this regard, thecontainer 182 may include retaining means (not shown) for maintaining each of the plurality oftrial implants 184. For example, the retaining means may be a frame sized to frictionally receive an appropriately sized one of the plurality oftrial implants 184.

Thecontainer 182 is preferably a box having a cover (shown partially). Thecontainer 182 is preferably constructed from a rigid material able to withstand repeated sterilization. For example, thecontainer 182 may be formed from stainless steel able to maintain its structural integrity when repeatedly processed through an autoclave. Further, thecontainer 182 includes a plurality ofpassages 186 for facilitating sterilization of the plurality oftrial implants 184 when thetrial implant kit 180 is placed within a sterilization device, such as an autoclave.

The plurality oftrial implants 184 preferably are the various trial implants previously described. For example, the plurality oftrial implants 184 may include the rectangular trial implant 20 (FIG. 1), the tapered trial implant 60 (FIG. 2), the angled trial implant 100 (FIG. 3) and/or the reverse angle trial implant 140 (FIG. 4). As shown in FIG. 5, different sizes of each of the various trial implants (20, 60, 100, 140) are provided. It will be recalled that in preferred embodiments, the

trial implant

20, 60, 100 or 140 is preferably manufactured to assume different sizes. Each one of these different sizes may be placed within thecontainer 182. For example, three different sizes of theangled trial implant 100 are included in FIG. 5, having maximum widths of approximately 0.23 inch (5.8 mm), 0.29 inch (7.4 mm) and 0.37 inch (9.4 mm), respectively. An equal, greater or lesser number of other trial implants (e.g., therectangular trial implant 20, the taperedtrial implant 60 and/or the reverse angle trial implant 140) can also be provided. In other words, thetrial implant kit 180 depicted in FIG. 5 is only one example of an acceptable kit. As will be made clear below, thetrial implant kit 180 may contain as few as two, or more than one hundred, trial implants.

In conjunction with the differently sized and shaped trial implants comprising the plurality oftrial implants 184, thecontainer 182 preferably includes identification indicia 188. The identification indicia 188 is associated with each of the plurality oftrial implants 184 and preferably provides a user with an indication of the shape and size characteristics of a particular trial implant. The identification indicia 188 is preferably formed on thecontainer 182 adjacent a respective one of the retaining means (not shown). For example, the identification indicia 188 may include a reference to a shape of a particular one of the plurality of trial implants 184 (such as rectangular, tapered, angled and/or reverse angle), a height of the particular one of the plurality oftrial implants 184 and a length of that trial implant. Thus, the identification indicia 188 will be different for each one of the plurality oftrial implants 184. It will be obvious to one of ordinary skill in the art that a wide variety of identification indicia 188 can be utilized to identify the shape and/or size of a particular trial implant.

One important feature of thetrial implant kit 180 is that it can be repeatedly sterilized. For example, following the use of one or more of the plurality oftrial implants 184 to evaluate a disc space (described in greater detail below), all of the plurality oftrial implants 184 are placed at an appropriate location within thecontainer 182. The entiretrial implant kit 180 is then processed through a sterilization device (not shown), such as an autoclave. The autoclave effectuates sterilization of thetrial implant kit 180 by subjecting thetrial implant kit 180 to pressurized steam. The autoclave is normally fitted with a gauge that automatically regulates an internal pressure, and therefore the degree of heat to which thetrial implant kit 180 is subjected. Notably, thecontainer 182 includes the plurality ofpassages 186 to allow the pressurized steam to interact with the plurality oftrial implants 184. Following sterilization,trial implant kit 180 is removed from the sterilization device and is available for subsequent use. Thus, thetrial implant kit 180, including the plurality oftrial implants 184, can be repeatedly used to evaluate multiple disc spaces because thetrial implant kit 180 can be resterilized after each use.

F. Method of Use

One preferred method of using the

trial implant

20, 60, 100 or 140 of the present invention is shown in FIGS. 6-10. As shown in FIGS. 6-10, the

trial implant

20, 60, 100 or 140 is used to evaluate a damageddisc space 200. For example, the

trial implant

20, 60, 100 or 140 may be used to determine whether a similarly sized prosthetic spinal disc nucleus will "fit" within thedisc space 200. Thedisc space 200 separates twoadjacent vertebrae 202 and includes ananulus 204 and a nucleus region 206 (shown best in FIGS. 8 and 9). Posterior access to theanulus 204 is achieved by performing a laminotomy in a targetedlamina area 208. The laminotomy is normally performed adjacent anopening 210 formed in theanulus 204. Theopening 210 may be a naturally occurring tear in the anulus 204 (for example, where thedisc space 200 has herniated). Alternatively, theopening 210 may be created in theanulus 204 following the laminotomy, such as by removing a plug of material from theanulus 204. Even further, theopening 204 may be generated by creating a retractable flap in theanulus 204. Regardless of the exact configuration, theopening 210 provides access to thenucleus region 206. Excess nucleus material is removed from the nucleus region orcavity 206 to provide room for implantation of a prosthesis.

The surgeon then selects an appropriately sized trial implant for placement within thenucleus cavity 206. For example, the surgeon may be provided with the trial implant kit 180 (FIG. 5) containing the plurality of trial implants 184 (FIG. 5). The particular trial implant selected by the surgeon will depend upon a general estimate of the size of thenucleus cavity 206 based upon the patient's (not shown) height, weight and spinal extension. Further, the surgeon's trial implant selection will vary depending upon the particular location of the disc space 200 (for example, between the L4 and L5 vertebrae, between the L5 and S1 vertebrae, etc.) and whether the prosthetic spinal disc nucleus corresponding to the particular trial implant will be positioned at ananterior area 212 orposterior area 214 of thenucleus cavity 206. As an additional selection aide, a depth caliper may be employed to estimate the transverse diameter of thenucleus cavity 206 at theanterior area 212 or theposterior area 214. Even further, a contrast material may be injected into thenucleus cavity 206 and viewed via a fluoroscope. With this criteria in mind, any one of the previously described trial implants, including the rectangular trial implant 20 (FIG. 1), the tapered trial implant 60 (FIG. 2), the angled trial implant 100 (FIG. 3) or the reverse angle trial implant 140 (FIG. 4) are available. Further, it should be understood that for each one of the

trial implants

20, 60, 100 or 140 described, a variety of different sizes may be available. For example, the surgeon may first determine that thedisc space 200 requires implantation of the tapered prostheticspinal disc nucleus 90 of FIG. 2C at theanterior area 212 of thenucleus cavity 206. Based upon the patient's size and weight (and potentially in conjunction with measurements taken with a depth caliper), the surgeon will select the largest taperedtrial implant 60 he or she believes will fit at theanterior area 212.

Once a trial implant has been selected, the surgeon then attempts to insert that trial implant into thenucleus cavity 206. FIG. 8 depicts partial insertion of the taperedtrial implant 60 into thenucleus cavity 206. As shown in FIG. 8, the taperedtrial implant 60 is directed through theopening 210 in theanulus 204. Where theopening 210 in theanulus 204 is properly sized, theanterior side face 72 and the posterior side face 74 will not contact (or will "clear") theanulus 204 tissue defining the lateral walls of theopening 204. Typically, thesuperior face 68 and the inferior face 70 (FIG. 2) will be in contact with theanulus 204 tissue and are therefore relatively smooth to facilitate movement along theanulus 204.

The surgeon continues to move the taperedtrial implant 60 distally into thenucleus cavity 206 until the entire taperedtrial implant 60 is within thenucleus cavity 206. The surgeon then attempts to rotate the taperedtrial implant 60 ninety degrees to the position shown in FIG. 9. Once rotated, the surgeon attempts to forcibly position the tapered trial implant to a desired area of thenucleus cavity 206, such as theanterior area 212. This may include the use of a separate force applying tool. As previously described, by utilizing a tough material, the

trial implant

20, 60, 100 or 140 will not alter in shape in response to this auxiliary force. The relatively smooth nature of thesuperior face 68 and the inferior face 70 (FIG. 2) promotes movement of the taperedtrial implant 60 between the adjacent vertebrae 202 (FIG. 7).

As depicted in FIG. 9, the taperedtrial implant 60 extends transversely across thedisc space 200, adjacent theanterior area 212 of thenucleus cavity 206. The anterior side face 72 is adjacent a portion of theanulus 204, whereas the posterior side face 74 is centrally located within thenucleus cavity 206. This positioning is likewise depicted in FIG. 10. Once again, the taperedtrial implant 60 has been positioned adjacent theanterior area 212 of thenucleuscavity 206. Thesuperior face 68 is adjacent an upper one of the opposingvertebrae 202, whereas theinferior face 70 is adjacent a lower one of the opposingvertebrae 202. If the surgeon is able to position the taperedtrial implant 60 as shown in FIGS. 9 and 10, the surgeon can confidently conclude that a similarly sized prosthetic spinal disc nucleus (such as the tapered prostheticspinal disc nucleus 90 shown in FIG. 2C) will "fit" within theanterior area 212nucleus cavity 206 upon subsequent implantation. If desired, the surgeon may attempt to place a second trial implant (not shown) in theposterior area 214 of thenucleus cavity 206. Notably, the above-described procedure for inserting the taperedtrial implant 60 applies equally to other trial implant embodiments, such as the rectangular trial implant 20 (FIG. 1), the angled trial implant 100 (FIG. 3) and the reverse angle trial implant 140 (FIG. 4).

After the surgeon evaluates thedisc space 200 as described above, the trial implant is then removed from thenucleus cavity 206. In this regard, the trial implant is preferably provided with a retrieving means for facilitating removal from thedisc space 200. One example of a retrieval means 220 associated with theangled trial implant 100 is shown in FIG. 11. The retrieving means 220 depicted in FIG. 11 is a suture secured to thefirst tab 104 of theangled trial implant 100. Alternatively, a flexible thread or similar material may be used. During the above-described implantation procedure, a portion of the suture 220 remains exterior theanulus 204, passing through theopening 210. Theangled trial implant 100 is removed from thedisc space 200 by simply pulling on the suture 220. In response, the suture 220 guides theangled trial implant 100 toward theopening 210, such that theangled trial implant 100 extends in a generally sagitall direction within thenucleus cavity 206, generally aligned with theopening 210. At a certain point during retraction of the suture 220, thefirst tab 104 and thefirst end face 116 of theangled trial implant 100 will be exposed through theopening 210 in theanulus 206. From this position, the surgeon is able to grasp thefirst tab 104 and remove theangled trial implant 100 from thedisc space 200.

An alternative approach for retrieving the trial implant is depicted in FIG. 12. More particularly, FIG. 12 shows therectangular trial implant 20 and aretrieval tool 230. Theretrieval tool 230 includes ahandle 232 and ashank 234. Theshank 234 includes aproximal portion 236 and a distal portion 238. The distal portion 238 extends from theproximal portion 236 to form a 90 degree angle, and terminates in ashoulder 240. The distal portion 238 of thetool 230 is sized to be selectively secured to thefirst tab 24 of therectangular trial implant 20. More particularly, the distal portion 238 of thetool 230 is sized to pass through theopening 40 in thefirst tab 24. Thus, in the embodiment shown in FIG. 12, thefirst tab 24, including theopening 40, constitutes a retrieving means. During use, the rectangular trial implant 20 (or any other trial implant embodiment) is retrieved by directing theshank 234 of thetool 230 toward therectangular trial implant 20. The distal portion 238 of thetool 230 is then directed through theopening 40 of thefirst tab 24. Once the distal portion 238 has passed through theopening 40, theshoulder 240 prevents the distal portion 238 from readily disengaging from thefirst tab 24. Once secured, theretrieval tool 230 is retracted from the disc space 200 (FIG. 9). Therectangular trial implant 20, via connection to thetool 230 at thefirst tab 24, is likewise retracted from thedisc space 200.

Yet another alternative embodiment of a retrieving means is shown in FIG. 13. FIG. 13 depicts a trial implant 250 (which may be a rectangular trial implant, tapered trial implant, angled trial implant, reverse angle trial implant or other embodiment) having acentral body 252 and opposingtabs 254. One of the opposingtabs 254 of the trial implant 250 is shown as presenting a grasping surface for grasping by a hemostat 256. Hemostats are well known in the art and generally comprise an elongated tool having a scissors-like distal end by which a surgeon may apply a compressive or pinching force. With the embodiment shown in FIG. 13, the opposingtabs 254 constitute retrieving means. During use, the surgeon (not shown) simply directs the hemostat 256 to grasp one of the opposingtabs 254 along the grasping surface. Once secured to the hemostat 256, the hemostat 256 and the trial implant 250 can be removed from the disc space 200 (FIG. 9). It should be recognized that a hemostat can also be used to assist in inserting the trial implant 250 as well. Importantly, because the trial implant 250 material is preferably tough, thetab 254 will not break away from the central body 250 when a shearing force is applied to thetab 254 by the hemostat 256. With the approach of FIG. 13, it should be understood that the opposingtabs 254 need not include the previously-described opening. Additionally, only one of the opposingtabs 254 is required to facilitate retrieval of the trial implant 250.

As described above, the trial implant of the present invention is used to evaluate various spacing considerations associated with a disc space. In this regard, FIGS. 8-10, along with the associated description, presented use of a trial implant that was properly sized for a particular disc space. One benefit of the present invention, however, is that a surgeon can also determine whether a particular trial implant is too large or too small for a particular disc space. For example, FIG. 14 depicts attempted insertion of atrial implant 260 into thedisc space 200. Thetrial implant 260 may be the rectangular trial implant 20 (FIG. 1), the tapered trial implant 60 (FIG. 2), the angled trial implant 100 (FIG. 3), the reverse angle trial implant (FIG. 4), or other similar designs. Thedisc space 200 includes the opposingvertebrae 202, theanulus 204 and thenucleus cavity 206. Theanulus 204 includes theopening 210. As shown in FIG. 14, thetrial implant 260 is too large to pass through theopening 210 in theanulus 204. In other words, as the surgeon (not shown) attempts to insert thetrial implant 260 through theopening 210, theanulus 204 impedes insertion into thenucleus cavity 206. During this attempt, however, the surgeon will likely notice a spring-like resistance to insertion of thetrial implant 260. In this regard, thetrial implant 260 does not contact theadjacent vertebrae 202, which would otherwise provide a more definitive resistance or "hard stop" to movement of thetrial implant 260. Based upon this perception, the surgeon will determine that theopening 210 in theanulus 204 is too small to allow passage of thetrial implant 260, and therefore should attempt to enlarge theopening 210. After theopening 210 has been enlarged, a second attempt will be made to insert thetrial implant 260.

Another possible relationship between atrial implant 270 and thedisc space 200 is shown in FIG. 15. Once again, thetrial implant 270 may be any one of the

trial implants

20, 60, 100 or 140 previously described, or other design. Thetrial implant 270 is too large relative to thedisc space 200. As the surgeon (not shown) attempts to insert thetrial implant 270 through theopening 210 in theanulus 204, a portion of thetrial implant 270 contacts the opposingvertebrae 202. Due to the rigid nature of the opposingvertebrae 202, the surgeon will sense a hard stop to movement of thetrial implant 270. Under these circumstances, the surgeon will conclude that thetrial implant 270 is too large for thedisc space 200, and will subsequently attempt to insert a differently sized trial implant.

In addition to having a height greater than a height of the opening 210 (as shown in the example of FIG. 14), the trial implant may also be too wide for theopening 210. This problem is represented in FIG. 16, which includes atrial implant 280 and thedisc space 200. Once again, thetrial implant 280 may be any one of the

trial implants

20, 60, 100 or 140 previously described. As shown in FIG. 16, thetrial implant 280 is wider than theopening 210 in theanulus 204. Under these circumstances, assuming the trial implant does not contact the opposing vertebrae 202 (FIG. 15), the surgeon will sense a spring-like resistance as thetrial implant 280 contacts theanulus 204. Based on a visual evaluation of thedisc space 200, the surgeon will determine that theopening 210 is too small and requires enlargement. Once theopening 210 has been enlarged, a second attempt will be made to insert thetrial implant 280.

Finally, it is possible that a particular trial implant may be too small for a particular disc space. An example of this scenario is shown in FIG. 17 which includes a trial implant 290 (which may be any one of the previously described

trial implants

20, 60, 100 or 140) implanted within thedisc space 200. Where thetrial implant 290 is too small for theparticular disc space 200, thetrial implant 290 will easily slide to theanterior area 212 of thenucleus cavity 206. In other words, thetrial implant 290 does not "tightly" fit between theadjacent vertebrae 202. When the surgeon senses that thetrial implant 290 is too small, thetrial implant 290 is removed from thedisc space 200. Subsequently, an attempt is made to implant a larger trial implant and again evaluate its relationship to a size of thedisc space 200.

The trial implant of the present invention provides an inexpensive, reusable device for evaluating a disc space. Because the trial implant closely resembles, in terms of shape and size, an available prosthetic spinal disc nucleus, a surgeon is able to quickly ascertain whether that prosthetic spinal disc nucleus will "fit" within a disc space. In this regard, once the trial implant has been used to evaluate the disc space, the trial implant can be sterilized and reused. Finally, by providing a kit containing a number of differently sized trial implants, a surgeon can determine with relative confidence the size of a prosthetic spinal disc nucleus required by a particular disc space.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, while the trial implant has been described with reference to rectangular, tapered, angled, and reverse angled shapes, other designs are equally acceptable. So long as the trial implant resembles an available prosthetic spinal disc nucleus, that trial implant can be used to evaluate whether or not the particular prosthetic spinal disc nucleus will fit within the disc space. Similarly, the various trial implant embodiments have each included two opposing tabs. These tabs have been provided to resemble a stitching feature associated with one available form of a prosthetic spinal disc nucleus. Thus, with reference to a prosthetic spinal disc nucleus that does not include any lateral extensions, one or both of the opposing tabs can be eliminated. Additionally, the various faces of the trial implants have all been described as preferably being relatively smooth. To facilitate insertion of the trial implant, however, it is only necessary that the superior and inferior face be relatively smooth. Even further, in some instances, all faces may be relatively rough yet the trial implant will still perform the desired evaluation function.